It’s been 90 years since someone with a criminal conviction was elected to the House. But one felon could jump-start his congressional comeback if he wins a Republican primary next week.

GOP voters in New York’s 11th District head to the polls Tuesday to choose between Rep. Dan Donovan and former Rep. Michael G. Grimm, who resigned his seat in early 2015 and served seven months in prison after pleading guilty to tax evasion.

While Donovan has referenced Grimm’s conviction as an example of the former lawmaker’s dishonesty, much of their primary battle has centered on who represents the better ally for President Donald Trump. The president is popular in the district, where his brash style appeals to voters in the ‘Forgotten Borough’ of Staten Island.

Trump has weighed in on the primary, backing Donovan, but Tuesday’s election could be a test of the president’s political power among his base supporters. And the GOP primary result could determine whether the seat is in more danger of a Democratic takeover come November.

Watch: Can a Felon Make a Congressional Comeback? What to Watch in New York’s 11th District Primary

‘Trump country’

Both campaigns are confident heading into the final week of the race, but Donovan’s team sees the Trump endorsement as a critical development.

“The race has really started to crystalize and I think part of that is the president really weighing in,” Donovan campaign spokeswoman Jessica Proud said. “I think Grimm’s entire campaign was really undercut by that endorsement because it was basically the main rationale for his candidacy.”

A source familiar with discussions indicated there could be more involvement from the president in the coming days, but nothing has been solidified.

Outside groups have also gotten involved in boosting Donovan, including the pro-Trump super PAC America First Action.

The political arm of the Republican Main Street Partnership, which describes itself as representing the GOP’s “governing wing,” has also backed Donovan, who is a member of the group. (Grimm is also a former member). Main Street Partnership has spent money on digital ads, websites and canvassing efforts. The U.S. Chamber of Commerce also launched a television ad touting Trump’s endorsement.

“You have to remember, Staten Island is hardcore Republican and conservative,” said GOP strategist Susan del Percio, who is not involved with either campaign. “So [Trump’s endorsement] really does work in this district.”

Trump carried the 11th District, which includes Staten Island and parts of Brooklyn, by 10 points in 2016. Republican operatives say his style and stances on issues such as immigration appeal to voters there.

A Grimm supporter involved in the local party described the “political culture” of the district as “one of fundamental mistrust of the powers that be, fundamental mistrust of the establishment and ‘big government.’”

That supporter also said Grimm speaks to that culture and has a similar fast-talking, “take-no-prisoners” style.

Grimm campaign spokesman Joe Shikhman said Trump’s endorsement had not had a major effect on the former congressman’s bid.

“People love the president, people voted for the president. … But they have agreed to disagree with the president on this one,” he said.

The local Grimm supporter described the mindset of people backing the former congressman as, “I don’t care, he’s my guy.”

“They feel like they’re making a statement with a vote for Michael Grimm,” the Republican said. “It’s a big middle finger to the Justice Department”

Grimm has echoed the president in describing his own conviction as a partisan witch hunt. Donovan, who succeeded Grimm in 2015, has said his predecessor betrayed voters by declaring his innocence when he ran for re-election the previous year and won while under indictment.

Shikhman said the Grimm campaign has continued to argue that Donovan does not support Trump’s agenda despite the president weighing in. Grimm has pointed to the incumbent’s votes against the GOP tax overhaul and the bill repealing much of the 2010 health care law. But Donovan said those bills would have hurt the district, and pointed to his votes as evidence that he puts his constituents first.

Grimm future?

When Grimm entered the race last fall, Republicans immediately viewed him as a threat, despite his time behind bars.

“As soon as he announced, he’s a credible threat because he’s a former member and he’s got almost 100 percent name ID,” said Sarah Chamberlain, the president of the Republican Main Street Partnership.

“He is very good on the campaign trail,” del Percio said. “That’s why Michael’s a threat. He works very hard and he is charming on the campaign trail and people do know him.”

Grimm was ahead by 10 points in the only public poll in the race from Siena College and NY1, released earlier this month, but it was mostly conducted before Trump’s endorsement.

“It’s a hard district for a Democrat to win, but in an off-year, it’s not impossible,” Del Percio said. “And the Republicans shouldn’t make it easier by putting in an ex-felon.”

Democrats still have to pick their candidates in the race, but the national party sees Army veteran Max Rose as a strong contender. He ended the pre-primary reporting period with more than $1 million in his campaign coffers.

Democrats have a voter registration edge in the 11th District, 46 percent to 27 percent over Republicans. Twenty-two percent of voters aren’t registered with any party.

Grimm’s team contends his conviction would not be a problem in the general, and point out that voters still supported him in 2014 while he was under indictment. His supporters also argue it’s Donovan who would be the weaker general election candidate, noting that he is still struggling in the primary despite the backing of Trump and local party leaders and help from outside groups.

“To say that that person is the stronger candidate, it just doesn’t make sense at all,” Shikhman said. “He has clearly lost his base.”

Operatives on both sides expected the GOP primary next week to be close, noting that turnout was difficult to predict.

“There have been too many surprises this cycle to try to predict what’s to happen next Tuesday,” one national GOP strategist said.